The polygalactomannans are polysaccharides composed principally of galactose and mannose units and are usually found in the endosperm of leguminous seeds, such as guar, locust bean, honey locust, flame tree, and the like. Guar flour, for example, is composed mostly of a galactomannan which is essentially a straight chain mannan with single membered galactose branches. The mannose units are linked in a 1-4-.beta.-glycosidic linkage and the galactose branching takes place by means of a 1-6 linkage on alternate mannose units. The ratio of galactose to mannose in the guar polymer is, therefore, one to two. Guar gum has a molecular weight of about 220,000.
Locust bean gum is also a polygalactomannan gum of similar molecular structure in which the ratio of galactose to mannose is one to four. Guar and locust bean gum are the preferred sources of the polygalactomannans, principally because of the commercial availability thereof.
Polygalactomannan gums swell readily in cold water and can be dissolved in hot water to yield solutions which characteristically have a high viscosity even at a concentration of 1-1.5 percent. Guar gum and locust bean gum as supplied commercially usually have a viscosity (at 1% concentration) of around 1000 to 4000 centipoises at 25.degree. C. using a Brookfield Viscometer Model LVF, spindle No. 2 at 6 rpm.
For a number of commercial applications it is advantageous to have a gum that provides a solution viscosity lower than that imparted by the same gum in the form in which it is ordinarily sold commercially. Thus, for various food products wherein a polygalactomannan is incorporated as a thickener or is used in a gel or jelly-type product, it is desirable to employ a gum which has a one percent solution viscosity between about 1000 and 2000 centipoises at 25.degree. C. Solutions having lower viscosities than those produced with conventional commercial gum are also advantageous in paper making procedures, either in the beater or when used as a sizing. Low viscosity solutions of polygalactomannan gums also find special application in the sizing and printing of textiles.
There are various other rigorous applications that require greater stability under variable conditions than is provided by hydrocolloid gums that are commercially available. For example, it is desirable that a gum which functions as a protective colloid or gelling agent in oil well drilling mud compositions and oil well fracturing compositions exhibit a degree of solution stability and heat stability under operating conditions.
Further, solutions of ordinary hydrocolloid gums are not sufficiently stable under variable conditions of pH and temperature or not sufficiently stable in the presence of polyvalent metal ions, to qualify for general application in the textile industry for sizing, printing and finishing operations, or in the paper industry as sizing and coatings agents.
Accordingly, it is a main object of the present invention to provide a process for producing hydrocolloid gums having improved properties for applications in petroleum, textile, printing, paper, food and pharmaceutical industries.
It is another object of the present invention to provide an improved process for producing polygalactomannan ether derivatives.
It is another object of the present invention to provide guar gum and locust bean gum compositions containing alkyl ether substituents.
It is a further object of the present invention to provide aqueous guar gum and locust bean gum compositions which are superior in solution stability and heat stability in comparison with unmodified guar gum and locust bean gum.
Other objects and advantages shall become apparent from the following description and examples.